[jira] [Commented] (SPARK-5464) Calling help() on a Python DataFrame fails with "cannot resolve column name __name__" error

["Apache Spark (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-5464?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14297842#comment-14297842 ] 

Apache Spark commented on SPARK-5464:
-------------------------------------

User 'JoshRosen' has created a pull request for this issue:
https://github.com/apache/spark/pull/4278

> Calling help() on a Python DataFrame fails with "cannot resolve column name __name__" error
> -------------------------------------------------------------------------------------------
>
>                 Key: SPARK-5464
>                 URL: https://issues.apache.org/jira/browse/SPARK-5464
>             Project: Spark
>          Issue Type: Bug
>          Components: PySpark, SQL
>    Affects Versions: 1.3.0
>            Reporter: Josh Rosen
>            Assignee: Josh Rosen
>            Priority: Blocker
>
> Trying to call {{help()}} on a Python DataFrame fails with an exception:
> {code}
> >>> help(df)
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
>   File "/Users/joshrosen/anaconda/lib/python2.7/site.py", line 464, in __call__
>     return pydoc.help(*args, **kwds)
>   File "/Users/joshrosen/anaconda/lib/python2.7/pydoc.py", line 1787, in __call__
>     self.help(request)
>   File "/Users/joshrosen/anaconda/lib/python2.7/pydoc.py", line 1834, in help
>     else: doc(request, 'Help on %s:')
>   File "/Users/joshrosen/anaconda/lib/python2.7/pydoc.py", line 1571, in doc
>     pager(render_doc(thing, title, forceload))
>   File "/Users/joshrosen/anaconda/lib/python2.7/pydoc.py", line 1545, in render_doc
>     object, name = resolve(thing, forceload)
>   File "/Users/joshrosen/anaconda/lib/python2.7/pydoc.py", line 1540, in resolve
>     name = getattr(thing, '__name__', None)
>   File "/Users/joshrosen/Documents/Spark/python/pyspark/sql.py", line 2154, in __getattr__
>     return Column(self._jdf.apply(name))
>   File "/Users/joshrosen/Documents/Spark/python/lib/py4j-0.8.2.1-src.zip/py4j/java_gateway.py", line 538, in __call__
>   File "/Users/joshrosen/Documents/Spark/python/lib/py4j-0.8.2.1-src.zip/py4j/protocol.py", line 300, in get_return_value
> py4j.protocol.Py4JJavaError: An error occurred while calling o31.apply.
> : java.lang.RuntimeException: Cannot resolve column name "__name__"
> 	at org.apache.spark.sql.DataFrame$$anonfun$resolve$1.apply(DataFrame.scala:123)
> 	at org.apache.spark.sql.DataFrame$$anonfun$resolve$1.apply(DataFrame.scala:123)
> 	at scala.Option.getOrElse(Option.scala:120)
> 	at org.apache.spark.sql.DataFrame.resolve(DataFrame.scala:122)
> 	at org.apache.spark.sql.DataFrame.apply(DataFrame.scala:237)
> 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
> 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> 	at java.lang.reflect.Method.invoke(Method.java:606)
> 	at py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:231)
> 	at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:379)
> 	at py4j.Gateway.invoke(Gateway.java:259)
> 	at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:133)
> 	at py4j.commands.CallCommand.execute(CallCommand.java:79)
> 	at py4j.GatewayConnection.run(GatewayConnection.java:207)
> 	at java.lang.Thread.run(Thread.java:745)
> {code}
> Here's a reproduction:
> {code}
> >>> from pyspark.sql import SQLContext, Row
> >>> sqlContext = SQLContext(sc)
> >>> rdd = sc.parallelize(['{"foo":"bar"}', '{"foo":"baz"}'])
> >>> df = sqlContext.jsonRDD(rdd)
> >>> help(df)
> {code}
> I think the problem here is that we don't throw the expected exception from our overloaded {{getattr}} if a column can't be found.
> We should be able to fix this by only attempting to call {{apply}} after checking that the column name is valid (e.g. check against {{columns}}).



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